There are various applications for which wide band transmitting and receiving antennas are required. These include applications in fields such as medical imaging, radar, radio frequency crystallography and telecommunications.
One type of antenna which is used in such applications are microstrip antennas. A typical microstrip antenna is fabricated by forming a shaped metallized layer on a planar circuit board substrate. Another metallized layer on the substrate serves as a ground plane. U.S. Pat. No. 5,036,335 describes an example of a microstrip antenna.
A balanced stripline antenna is similar to a microstrip antenna except that it has a pair of ground planes, one on each side of the active element. Guillanton et al. A new design tapered slot antenna for ultra-wideband applications Microwave and Optical Technology Letters v. 19, No. 4, November 1998 discloses a balanced antipodal Vivaldi antenna made using stripline technology.
Microstrip and stripline antennas suffer from the disadvantage that the dielectric substrate materials on which the metallized layers are supported adversely affect the radiation characteristics of the antennas at certain frequencies.
There is a need for antennas capable of transmitting, receiving and/or receiving and transmitting over a wide frequency range.